In a rotating machine such as a steam turbine, a gas turbine, or the like, in order to prevent leakage of a working fluid such as steam or the like from a gap formed between a stationary side (a casing) and a rotary side (a rotor blade), a seal mechanism is used (for example, see Patent Literature 1).
For example, in order to reduce the working fluid that passes stator blades from passing through the gap (a rotor blade tip cavity) between the rotor blade and the casing, for example, a technology of forming a seal member such as a sealing fin or the like extending from an inner circumference of the casing toward the rotor blade is known.